Apparently this is a rebranded Philips, based on its construction & etch. It also lights more yellow than other HPS lamps I have so am not very fond of it.
I don't remember seeing purple flashes when I lit it. But I have had regular HPS lamps show the sparky the purple flashes at startup too...I think that's just stuff sputtering off the electrodes.
Yeah I've seen mercury-containing HPS lamps start off purplish for a couple seconds too. My favorites are the ones that start off similar to clear MVs before shifting toward orange.